Formation-sampling apparatus



March 4, 1969 FJELDS. 3,430,715

FORMATION- SAMPLING APPARATUS Filed June 29, 1967 Foyer Q. 59/0;

INVENTOR.

7 Claims ABSTRACT OF THE DISCLOSURE The particular embodiment described herein as illustrative of one form of the invention is directed to borehole apparatus for obtaining and collecting a plurality of elongated samples from earth formations traversed by the borehole. To accomplish this, the disclosed tool includes cutting wheels that are arranged to be extended and make cuts along the face of an adjacent formation as a carrier supporting the wheels is moved longitudinally. By means of particularly-arranged guide systems, the cutting wheels will be guided in a path conforming to any irregularities on the surface of the borehole wall from which the sample is being taken.

Accordingly, as will subsequently become more apparent, the present invention pertains to new and improved earth formation sample-taking apparatus; and, more particularly, this invention relates to sample-taking apparatus for obtaining continuous samples of earth formations along irregularly formed Wall surfaces of a previously drilled borehole.

Heretofore, formation samples have usually been obtained from previously drilled boreholes by explosively propelling into the adjacent wall of a borehole one or more tubular bodies or so-called bullets having appro priately arranged forward cutting edges. As these bullets penetrate the borehole Wall, a generally cylindrical core of the formation material is driven into each bullet so that, when the bullets are subsequently retrieved, the cores in each will be recovered at the surface for examination. Typical of such core-taking bullets are those shown in Patents Nos. 2,678,804, 2,923,530, 3,072,202 and 3,220,490.

It is recognized, of course, that although such coretaking bullets have been highly successful, the most ideal arrangement would be to obtain a continuous sample of an earth formation from along a substantial vertical interval of a borehole. Heretofore, this has not been commercially feasible at least from boreholes that have been previously drilled.

One tool as shown in Patent No. 3,173,500 has been proposed, however, in which a pair of rotatable cutting wheels are cooperatively arranged to be extended outwardly to cut their way into an adjacent formation. Then, as they are slowly raised, the cutting wheels will cut a single elongated wedge-shaped formation sample out of the borehole wall. This sample is caught by the tool and returned to the surface. To elevate the cutting wheels of this tool and their driving motor, a large piston is disposed in an elongated piston cylinder and connected to the driving motor by a lon shaft extending out of the lower end of the piston chamber. A hydraulic fluid is confined in the hydraulic chamber above the piston and initially prevented from entering an empty dump chamber in the tool by a remotely operated normally-closed valve.

When the driving motor and cutting wheels in this patented tool are to be elevated, the remotely operated valve is opened so that the hydrostatic pressure of the borehole fluids acting on the exposed face of the piston States Patent will pull the driving motor upwardly as the hydraulic fluid is slowly displaced by the piston into the dump chamber. An outwardly projecting guide pin on the motor is received in a somewhat U-shaped narrow guide slot in the support, which slot is arranged to extend the cutting wheels and then retract them at the end of the travel of the driving motor. It is, of course, apparent that this tool can obtain only one formation sample during a single trip into a borehole. Moreover, it is further apparent that since the cutting wheels can follow only a predetermined vertical path, a depression in the borehole wall will result in little or no sample being obtained from the corresponding formation interval.

Accordingly, it is an object of the present invention to provide a new and improved core-slicing tool that is capable of taking formation samples from the sidewalls of a borehole irrespective of the condition of the wall surfaces of the borehole.

This and other objects of the present invention are obtained by arranging a suitable prime mover to move longitudinally relative to a support. Formation-cutting means, such as a cooperatively arranged pair of rotatable cutting wheels, are connected by power-transmission means to the prime mover. Guide means, such as appropriately arranged channels or grooves on one of the relatively movable members and cooperative guide pins on the other of the relatively movable members, are provided so that the cutting wheels are successively extended, moved along a vertical cutting path, and then retracted as the prime mover travels longitudinally in relation to the support. The guide grooves are further arranged so that when the cutting wheels are extended, the wheels are free to move between certain lateral limits. Accordingly, the present invention includes means for normally urging the cutting wheels outwardly and means adapted to engage the borehole wall and, as any irregularities thereon are encountered, to shift the cut-ting wheels correspondingly to obtain a continuous sample.

The novel features of the present invention are set forth with particularity in the appended claims. The operation together with further objects and advantages thereof, may best be understood by way of illustration and example of certain embodiments when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 depicts a core-slicing tool arranged in accordance with the present invention in a borehole and in position to obtain an elongated formation sample;

FIGURE 2 is a schematic representation of the intermediate portion of the tool shown in FIGURE 1;

FIGURE 3 is a schematic representation of one arrangement of a groove system arranged in accordance with the present invention;

FIGURE 4 is .a cross-sectional view taken along the lines 4-4 in FIGURE 3;

FIGURE 5 is an elevational view of one portion of a preferred embodiment of the core-slicing tool shown in FIGURES 1 and 2; and

FIGURE 6 is a cross-sectional view taken along the lines 66 of FIGURE 5.

Turning now to FIGURE 1, a core-slicing tool 10 arranged in accordance with the present invention is shown suspended from a cable 11 in a borehole 12 and in position to obtain an elongated prismatic or wedgeshaped sample 13 from the adjacent wall of an earth formation 14. As seen in FIGURE 1, the tool 10 is preferably comprised of a number of tandemly connected housings 1519 suitably arranged for enclosing the various components to the tool. The upper housing 15 pre'ferably encloses typical circuitry for locating the tool 10 at a desired position in the borehole 12 as well as circuitry for controlling the various components in the tool and transmitting power as well as information relating to the operation and position of the tool through the various conductors in the suspension cable 11.

The next lower housing 16 preferably includes suitable longitudinally spaced, hydraulically actuated pistons 20 for selectively extending a wall-engaging member 21 on the rear of the tool laterally against one side of the borehole 12 to shift the forward face of the coreslicing tool in the opposite direction. In one manner of making the wall-engaging member 21 selectively operable from the surface, a hydraulic pump 22 and chamber 23 (shown only schematically) are arranged to extend the wall-engaging member whenever hydraulic fluid is pumped into the piston chambers behind the pistons and to retract the wall-engaging member whenever hydraulic fluid is pumped into the piston chambers ahead of the pistons. It will be realized, of course, that by maintaining an increased hydraulic pressure behind the pistons 20, the wall-engaging member 21 will urge the forward face of the tool 10 against one wall of the borehole 12 with a corresponding force. The particular arrangement selected is of little consequence so long as the forward face of the tool 10 is near or against the borehole wall as the formation sample, such as at 13, is being taken.

The intermediate housing 17 of the tool 10 supports the selectively operable formation-sampling means 24 of the tool. As will subsequently be explained in greater detail with respect to FIGURES 2, 5 and 6, these formation-sampling means 24 include a pair of similar cutting wheels 25 that are respectively mounted in converging vertical planes and arranged to rotate about independent, outwardly diverging axes themselves lying generally in the same horizontal plane and intersecting each other at a suitable angle. A longitudinal opening 26 is provided along the forward wall of the housing 17 diametrically opposite from the wall-engaging member 21. The cutting wheels 25 are suitably arranged and sized in relation to one another so that, when extended, their peripheral edges will pass through the housing opening 26 and all but come together at about the point of intersection of the three aforementioned planes. Thus, by moving the wheels 25 in unison in a generally vertical direction, the generally wedge-shaped or triangular prismatic sample 13 will be cut from the adjacent formation 14.

To gain entrance for the cutting wheels 25 into the formation 14, the present invention includes guide means 27 (to be subsequently described) for advancing the wheels outwardly through the housing opening 26 and in an inclined direction until they have reached at least their minimum extended position. While making a longitudinal cut, the cutting wheels 25 are allowed to move between lateral positions and the guide means 27 will function to shift the cutting wheels in and out as irregularities are encountered on the borehole wall. Then, after a longitudinal cut of a predetermined length has been made, the guide means 27 return the cutting wheels 25 along an upwardly inclined path and back through the housing opening 26 until they are fully retracted. To return the cutting wheels 25 to their original starting position, the guide means 27 then direct the wheels in the opposite longitudinal direction while still maintaining them fully retracted.

The lower housing 19 of the tool 10 is arranged to receive a plurality of core samples and keep them segregated from one another. Generally speaking, the housing 19 is arranged in such a manner that a plurality of upright tubes therein (not shown) that are equally spaced about a rotatable axial shaft therein (not shown) will be sequentially positioned by motion-translating means in the housing .18 thereabove to successively receive a formation sample as the tool 10 is operated. These motion-translating means in the housing 18 are arranged to rotate the sample-receiving tubes one at a time into position for receiving a formation sample 13. In this manner, the tool 10 can be employed on a single trip in the borehole 12 to recover a large number of formation samples which are separately disposed in the compartments in a predetermined order. Inasmuch as the motion-translating means and sample receiver in the housings 18 and 19 are not part of the present invention and are fully described in copending applications Ser. Nos. 649,929 and 649,976 filed simultaneously herewith, it is believed that these portions of the tool 10 need no further description.

Turning now to FIGURE 2, a schematic representation is shown of the intermediate housing 17 of the tool 10 in which the formation-sampling means 24 and guide means 27 of the present invention are confined. In general, the formation-sampling means 24 include a housing or enclosure 28 that is adapted for longitudinal travel in opposite directions in relation to the tool housing 17. In one manner of accomplishing longitudinal travel of the enclosure 28 the enclosure is secured to one or, preferably, two tubular members 29 (both seen in FIGURE 6). These tubular members 29 are in turn slidably disposed about substantially longer, paralleled longitudinal rods 30 (both seen in FIGURE 6) that are secured only at their upper and lower ends to the tool housing 17 and spaced away from the rear wall thereof. Suitable packing means 31 are arranged on the opposite ends of the tubular members 29 for slidably sealing the interior of the tubular members around the elongated rods 30. Piston members 32 (only one shown in FIGURE 2) are respectively fixed at an intermediate position on each of the elongated rods 30 and slida-bly sealed relative to the internal bore of their associated tubular member 29 to define separate upper and lower fluid-tight chambers 33 and 34 therein above and below each fixed piston member.

Accordingly, it will be appreciated that by developing a higher fluid pressure in the upper chambers 33 than that in the lower chambers 34, the tubular members 29 and enclosure 28 connected thereto will be moved upwardly along the elongated rods 36 relative to the tool housing 17. Similarly, by imposing a higher pressure in the lower hydraulic chambers 34 than that in the upper hydraulic chambers 33, the enclosure 28 will travel downwardly along the rods 30.

To develop such higher pressures in the chambers 33 and 34, a suitable hydraulic pump 35 is mounted within the enclosure 28. Fluid lines 36 and 37 are respectively connected between the hydraulic chambers 33 and 34 and the pump 35. By selecting a reversible-type hydraulic pump 35 and filling the chambers 33 and 34 with a suitable hydraulic fluid, the pump can be selectively operated from the surface to transfer hydraulic fluid between the chambers to accomplish the desired travel of the enclosure 28 along the elongated rods 30.

By arranging a typical movable, but sealed, barrier such as a bellows or piston (neither shown) at a convenient point in a wall of the enclosure 28, the hydraulic fluid in the enclosure and the chambers 33 and 34 will be maintained at a pressure at least equal to the hydrostatic pressure of fluids or so-called *mud" in the borehole 12. In this manner, by pressure-balancing the hydraulic system relative to the borehole hydrostatic pressure, the hydraulic pump 35 needs only to develop a pressure suflicient to overcome the weight of the enclosing 28 and whatever friction there may be encountered in moving the cutting wheels 25 and enclosure.

Although other prime movers can be used, it is preferred to operate the pump 35 by a submerisble reversibletype electric motor 38 of suitable dimensions to conveniently fit into the enclosure 28. Electrical conductors (not shown) are connected as required between the motor 38 and controls (not shown) in the upper housing 15 (FIG- URE l) for controlling the motor, with these conductors, of course, being fluidly sealed where they pass through the walls of the sealed enclosure 28.

To power the cutting wheels 25, the formation-sampling means 24 include a prime mover, preferably an electrical motor 39, which is also fitted into the enclosure 28 and its shaft connected to the cutting wheels by suitable power-transmission means, such as a universal joint which is connected by way of another shaft 41 to a rightangle gear drive 42 (FIGURE 6) having outwardly diverging wheel shafts 43 at an angle to one another. It will be appreciated that by locating the cutting wheel motor 39 in the enclosure 28, it will also be pressurebalanced in the same manner as the pump motor 38. Similarly, as best seen in FIGURE 6, by enclosing the motor shaft, the shaft 41 and universal joint 40 in an oil-filled conduit, such as a tube 43 that is fluidly sealed at its opposite ends to the enclosure 28 and gear drive 42 and in fluid communication with each, the powertransmission means will also be pressure-balanced.

A pair of depending arms 44 disposed on opposite sides of the protective tube 43 are connected at their lower ends to the gear drive 42 and pivotally connected at their upper ends to the enclosure 28 so as to pivot about an axis 45 lying generally in the same horizontal plane as the pivotal axis of the universal joint 49. As part of the guide means 27, outwardy projecting guides, such as spring-biased keys or pins 46 (both seen in FIGURE 6), on the pivoted arms 44 are slidably disposed in a labyrinth-like system of channels, such as slots or grooves 47 (only one system seen in FIGURE 2), that are formed in the interior side walls of the intermediate housing 17 on opposite sides of the longitudinal opening 26 therein. As will subsequently become apparent, these groove systems 47 are so arranged that upward longitudinal travel of the enclosure 28 from its full-line position to its dashedline position shown in FIGURE 2 will be effective (through the coaction of the guides 46 in the groove systems) to direct the cutting wheels 25 along the path AB-C depicted in FIGURES 2 and 3. Then, upon downward travel of the enclosure 28 back to the fullline position shown in FIGURE 2, the groove systems 47 and guides 46 will direct the cutting wheels 25 along the patch C-A towar dtheir initial position.

Turning now to FIGURE 3, a schematic representation is shown of one of the groove systems 47 arranged in accordance with the present invention. As seen there, the groove system 47 is arranged in a closed loop having two parallel longitudinal portions 48 and 49 of unequal length and spaced apart from one another. The shorter grooves 49 are connected at their opposite ends to the longer grooves 48 by oppositely-directed inclined grooves 59 and 51 which respectively intersect the longer grooves at longitudinally spaced intermediate points.

By directing the lower inclined grooves 50 upwardly and to the right (as viewed in FIGURES 2 and 3) toward the lower ends of the shorter longitudinal grooves 49, once the guide pins 46 are in the lower inclined grooves, upward travel of the enclosure 28 will carry the cutting wheels 25 outwardly as at B. Similarly, by directing the upper inclined grooves 51 upwardly and to the left (as viewed in the drawings) from the upper ends of the shorter grooves 4'9 to the longer grooves 48, further upward travel of the enclosure 28 will move the cutting wheels 25 along their path BC.

Accordingly, as the cutting wheels 25 move along the path AB, they will be moving upwardly and outwardly as they cut their way into the formation 14. Then, as the cutting wheels 25 move upwardly from their position at B, they will be cutting along a path of a length determined by the vertical height of the shorter grooves 49. Upon reaching the upper end of the grooves 49, the cutting wheels 25 will be retracted as they move further upwardly and cut their way toward their position at C. Thus, once the cutting wheels 25 have reached the position at C, a prismatic sample 13 with tapered ends will have been cut out of the formation 14 and will fall through the housing opening 26 and drop into the corereceiving housing 18 therebelow.

From the foregoing description it will be realized that the groove systems 47 must be arranged to insure that the guide pins 46 are diverted into the lower inclined grooves 58 as the enclosure 28 moves upwardly. Similar- 1y, when the enclosure 28 has reached its uppermost position, it is necessary that the guide pins 46 be prevented from re-entering the upper grooves 51 so that the cutting wheels 25 can proceed from their position at C back to their initial position at A. Otherwise, the cutting wheels 25 could return back along the path CB-A which might require that they cut their way back through the formation 14 should the tool 10 have shifted slightly.

Accordingly, means are provided to direct the guide pins 46 in a predetermined direction around the circuitous groove systems 47 but prevent these pins from moving in the opposite direction. As seen in FIGURES 3 and 4, stop means, such as an abutment 52, are provided in the lower end of each of the longer grooves 48 for preventing the guide pins 46 from entering the longer grooves as they move upwardly. To facilitate the passage of the guide pins 46, the abrupt faces of the abutments are extended along the line of the downwardly facing wall of the lower inclined grooves 50 as shown in FIGURE 3.

A similar problem will, of course, exist at the upper ends of the groove systems 47. Once the cutting wheels 25 have reached their position as shown at C, means must be provided to insure that the guide pins will remain in the longer grooves 48 and not re-enter the upper end of the upper inclined grooves 51 as the enclosure 28 is returned downwardly. An abutment 53 similar to that at 52 is, therefore, located across the entrance to the upper end of each of the upper inclined grooves 51. Hereagain, to facilitate the passage of the guide pins 46, the abrupt faces of the abutments 53 are made as a continuation of the right-hand (as viewed in FIGURE 3) side walls of the longer grooves 48.

It will be recognized that the abutments 52 and 53 must not, however, unduly hamper the passage of the guide pins 46 as they move in the correct directions around their respective groove systems 47. Thus, as best seen in FIGURE 4, the height of each abutment, as at 52, is less than the total depth of its associated groove 48 and an inclined surface or ramp, as at 54, is provided from the bottom of the groove 48 up to the upper surface of the abutment, with this inclined surface being located ahead of the abrupt face of the abutments in relation to the direction from which the guide pin 46 is intended to be coming. Thus, as the spring-biased guide pins 46 move downwardly in the grooves 48, for example, they will gradually retract as they move up the inclined ramps 54- of the abutments 52 as the enclosure 28 is moved downwardly. Once the guides 46 reach the abrupt abutment faces, the springs 55 (FIGURE 6) will urge them outwardly to return them to their normal extended position. The inclined surfaces or ramps 56 (FIGURE 3) on the lower ends of the upper abutments 53 in the slots 51 will, of course, function in the same manner.

The arrangement of the abutments 52 and 53 shown in FIGURE 3 will, therefore, positively direct the cutting wheels 25 along the path AB whenever the enclosure 28 is moved upwardly. The abrupt faces of the abutments 52 will, of course, prevent the guide pins 46 from continuing further upwardly in the longer grooves 48. Thus, once the guides 46 enter their respective lower inclined grooves 50, further upward travel of the enclosure 28 can only result in the cutting wheels 25 moving from their position at B to their position at C. Once the enclosure 28 has reached its upper limit of travel, the hydraulic pump 38 must, of course, be reversed to return the enclosure to its initial position. Upon downward travel, the guide pins 46 are, of course, prevented from re-entering the upper inclined grooves 51 by the abrupt surfaces of the upper abutments 53.

It will be appreciated from the drawings that so long as the guide pins 46 are in any of the narrow grooves 48, 5t) and 51, the cutting wheels 25 will be guided along a fairly well-defined path as determined by the configuration and width of the particular grooves that the guide pins are then in. On the other hand, it will be realized that so long as the guide pins 46 are in the wider longitudinal grooves 49, the cutting wheels 25 will be free to shift laterally between limits established by the transverse spacing between the inner and outer walls 57 and 58 of these wider grooves.

Thus, in accordance with the present invention, so long as the cutting wheels 25 are in the course of cutting along their path at B, the guide means 27 are so arranged that the cutting wheels will shift laterally to accommodate surface irregularities in the wall of the borehole 12. In addition to the previously mentioned widening of the longitudinal grooves 49 in relation to the transverse dimensions of the guide pins 46, means, such as a compression spring 59, are provided to normally urge the cutting wheels 25 outwardly with sufficient force to be effective. A guide member or skid plate 60 is preferably arranged on the forward face of the gear drive 42 to follow the contour of the wall surface of the borehole 12 and guide the cutting wheels 25 correspondingly as they are cutting away a formation sample 13. The extent of lateral deviation for the cutting wheels 25 will, of course, be directly related to the width of the wider longitudinal grooves 49 and the transverse dimensions of the guide pins 46.

Accordingly, with the guide means 27 of the present invention, the cutting wheels 25 are capable of removing a formation sample 13 (FIGURE 1) having a height determined by the effective longitudinal length of the grooves 50, 49 and 51. The depth of the cuts made by the cutting wheels 25, will, of course, be related to the spacing of the longitudinal grooves 48 and 49, with the inner walls 57 of the wider grooves establishing the minimum depth of the cuts and the outer walls 58 of the wider grooves establishing the maximum depth of the cuts. Thus, as the cutting wheels 25 are making a longitudinal cut, the guide member 69 will be held against the wall surface of the borehole 12 by the spring 59 to shift the cutting wheels laterally in response to surface irregularities.

Since the forward face of the tool 10 will be as close as possible to the wall of the borehole 12 once the wallengaging member 21 (FIGURE 1) is extended, it is preferred to so locate the inner walls 57 of the wider grooves 49 in relation to the longer grooves 48 that a formation sample 13 of maximum depth will be obtained when there are no depressions in the wall surface of the borehole 12. In this manner, as the cutting wheels 25 are moving along the path B-C whenever the guide member 60 encounters a depression in the wall surface of the borehole 12, the cutting wheels will be free to move further into the formation 14 (as at 61) at least until the guide pins 46 meet the outer walls 58 of the grooves 49.

Thus, the formation samples 13 will be of maximum thickness. The sample 13 will, of course, have irregular apicial edges corresponding to the variations in the borehole wall surfaces. It is believed, however, that this arrangement of the grooves 48 and 49 will give more reliable results since protrusions from the wall of the borehole 12 will establish how close the forward face of the tool 10 can be brought thereto. Moreover, it is more common to encounter depressions such as so-called washouts in a borehole wall than significant protrusions.

It should be recognized that the location of the guide pins 46 in relation to the pivotal axis 45 of the pivoted arms 44 and the axis of the cutting wheels 25 will determine the width of the wider grooves 49 as well as the spacing of the wider grooves from the longer grooves 48 to obtain a given size of a sample 13. For example, by locating the guide pins 46 midway between the pivotal axis 45 and the rotative axis of the cutting wheels 25, the cutting wheels will move outwardly twice as far as the spacing between the grooves 48 and 49. Similarly, once the cutting wheels 25 are extended, their span of lateral shifting will be twice the free lateral clearance of the guide pins 46 in the wider grooves 49. A multiplication factor of three could just as well be obtained by locating the guide pins 46 on the pivoted arms 44 at a point twice as far from the rotative axis of the cutting wheels 25 as the pins are from the pivotal axis 45 of the arms.

It will be noted in FIGURE 2 that the upper ends of the longer groves 48 extend a considerable distance above the junction of these groves with the upper inclined grooves 49. Although this extension of the longer grooves 48 is not required to guide the movements of the cutting Wheels 25, the enclosure 28 itself is further stabilized by providing longitudinally spaced lateral guides, as at 61 in FIGURE 5, thereon adapted to remain at all times in these longer longitudinal grooves. These guides 61 are always above the abutments 52 in the longer grooves 48 and will not, therefore, be prevented from moving either upwardly or downwardly in the grooves.

It will be recognized, of course, that it is desirable to have some indication at the surface of the progress of the formation-sampling means 24 during the course of samplerecovering operation. Even though the groove systems 47 depicted in FIGURES 2 and 3 necessarily require that the exact position of the cutting wheels 25 be known at all times, such knowledge is nevertheless of obvious b nefit to an operator at the surface.

Accordingly, as best seen in FIGURE 2 in one manner of providing indications at the surface representative of the longitudinal positions of the formation-samplin g means 24 in relation to the housing 17, an elongated tapered ramp 62 is secured to the housing in a convenient position that parallels the elongated rods 30. This tapered ramp 62 is suitably arranged to contact the outer end of a laterally movable actuator 63 that is connected to a variable electrical control 64 in the enclosure 28. It is, of course, preferred to mount the control 64 within the enclosure 28 and extend the actuator 63 through a suitable fluid seal (not shown) in the enclosure wall.

Thus, at all longitudinal positions of the enclosure 28 in relation to the housing 17 and the tapered ramp 62, the actuator 63 will assume corresponding lateral positions that are directly related to the distance between the particular point where the actuator is in contact with the ramp and either end of the ramp. By selecting a potentiometer, for example, as the control 64, it will be recognized that the resistance between the moving contact and one end thereof will vary in accordance with the movement of its actuator 63, with this resistance being directly related to the longitudinal distance between the present position of the enclosure 28 and its initial position as shown in FIGURE 2. This resistance will, of course, be constantly varied as the enclosure 28 moves in either direction in relation to the housing 17.

The varying resistance of the potentiometer 64 as the enclosure 28 moves could, of course, be measured directly at the surface to provide an indication of the present position of the formation-sampling means 24 at any given time. It is preferred, however, to employ electronic means which provide a more reliable surface indication. Accordingly, a circuit (not shown) that is more fully explained in copending applications Ser. Nos. 649,929 and 649,978 filed concurrently with the present application is employed. Since this circuit is fully explained in these copending applications and its details are not necessary to understand the present invention, it is believed necessary only to describe this circuit as being arranged to provide repetitive electrical pulses at the surface that have a pulse rate representative of the present longitudinal position of the formation-sampling means 24 in relation to the housing 17. As the enclosure 28 changes position in relation to the housing 17, the rate of these pulses will also change to provide a detectable indication at the surface characteristic of the new position of the formationsampling means 24.

Turning now to the operation of the present invention, the core-slicing tool 10 is first brought into position opposite a formation, as at 14, from which a sample 13 is desired. Once the tool is in position, the wall-engaging member 21 is extended to urge the forward face of the tool against the opposite wall of the borehole 12. As best seen in FIGURE 2, the motors 38 and 39 are then started and, once hydraulic pressure is applied to the upper chambers 33, the enclosure 28 will move upwardly in relation to the now-fixed housing 17.

As previously described with reference to the groove system 47, the cutting wheels 25 will be progressively moved upwardly through their various positions AB-C as the enclosure 28 moves toward its dotted-line position shown in FIGURE 2. Moreover, as the cutting wheels 25 move along the path B-C, the guide means 27 of the present invention will shift the cutting wheels inwardly and outwardly as irregularities in the wall surface of the borehole 12 are encountered by the guide member 60. As previously explained, this will allow the cutting wheels 25 to move further into the formation 14 as depressions are encountered in the wall of the borehole 12 to make it more likely that a usable sample 13 will be obtained along that particular interval of the formation.

Once the position indicator (not shown) at the surface that is connected to the potentiometer 64 indicates that the enclosure 28 is in its uppermost position, it will be assumed that a formation sample, such as at 13, has been cut and has fallen through the opening 26 and into a sample-receiving tube (not shown) in the lower housing 19.

When the enclosure 28 is at its uppermost position, the pump motor 38 is reversed to relieve the pressure in the upper hydraulic chambers 33 and allow the enclosure to return downwardly to its initial position. The position indicator will, of course, serve as a monitor to observe the progress of the enclosure 28 as the actuator 63 moves back down the tapered ramp 62. As explained in the aforementioned copending application Ser. No. 649,976, once the enclosure 28 has reached its lowermost position, another sample-receiving tube (not shown) will be brought into position for reception of another formation sample 13.

If more than one formation sample 13 is desired, the wall-engaging member 21 is retracted and the core-slicing tool 10 moved to another position in the borehole 12. Then, once the wall-engaging member 21 is again extended, the above-described procedure is repeated. Whenever a sufficient number of formation samples 13 are obtained, the tool 10 is then returned to the surface.

Accordingly, it will be appreciated that the present invention has provided a new and improved core-slicing tool capable of obtaining a plurality of formation samples from earth formations of interest. Moreover, by arranging the tool of the present invention with the guide system described herein, the cutting means will be positively guided and controlled at all times to follow any irregularities in the borehole wall.

While a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. Apparatus for obtaining samples of earth formations traversed by a borehole comprising: a support adapted for suspension in a borehole; formation-sampling means on said support and adapted for travel relative thereto between longitudinally-spaced positions, said formationsampling means including formation-cutting means adapted, when extended, to penetrate a borehole wall and cut away a formation sample therefrom; and guide means operable whenever said cutting means are in said extended position and adapted for shifting said cutting means laterally in accordance with irregularities in a borehole wall surface encountered -by said cutting means while cutting a formation sample.

2. The apparatus of claim 1 wherein said guide means include surface-engaging means for contacting such irregularities and moving said cutting means.

3. Apparatus for obtaining samples of earth formations traversed by a borehole comprising: a support adapted for suspension in a borehole; formation-sampling means on said support and adapted for travel relative thereto between longitudinally-spaced positions, said formation-sampling means including formation-cutting means adapted, when extended, to penetrate a borehole wall and cut away a formation sample therefrom; first guide means for selectively moving said cutting means laterally in relation to said support between a retracted position and an extended position to one side of said support in response to travel of said formation-sampling means from one of said spaced positions to another of said positions; and second guide means operable whenever said cutting means are in said extended position and adapted for shifting said cutting means laterally in accordance with irregularities in a borehole wall surface encountered by said cutting means while cutting a formation sample.

4. The apparatus of claim 3 wherein said second guide means include surface-engaging means for contacting such irregularities and moving said cutting means.

5. The apparatus of claim 4 wherein said first guide means include: first and second longitudinal channels spaced from one another on said support and facing said formation-sampling means, said second longitudinal channel being between said first longitudinal channel and said one side of said support; first and second transverse channels spaced from one another on said support and facing said formation-sampling means, one of said transverse channels interconnecting adjacent lower portions of said longitudinal channels and the other of said transverse channels interconnecting adjacent upper portions of said longitudinal channels; and a laterally-projecting guide member having a distal portion adapted for reception in said channels and operatively connected to said cutting means for moving said cutting means laterally between said retracted and extended positions as determined by the relative spacings of said channels.

6. The apparatus of claim 5 wherein said second longitudinal channel is wider than said first longitudinal channel to permit said guide member to shift laterally therein; and said second guide means include surface-engaging means for contacting such irregularities and moving said cutting means, and means normally urging said cutting means toward said extended position.

7. The apparatus of claim 6 wherein said cutting means include first and second cutting wheels respectively arranged in converging substantially vertical planes having an intersection to said one side of said support; and means supporting said cutting wheels for lateral movement between said retracted and extended positions.

References Cited UNITED STATES PATENTS 2,599,405 6/1952 Mennecier 78 X 3,154,147 10/1964 Lanmon l6655.1 3,173,500 3/1965 Stuart et al. 175-78 X 3,225,828 12/1965 Wisenbaker et al. l66-55 DAVID H. BROWN, Primary Examiner.

US. Cl. X.R. 

